Automatically trigger autocomplete on focus

src/public/app/services/note_autocomplete.js

@@ -217,6 +217,16 @@ function initNoteAutocomplete($el, options) {
     // clear any event listener added in previous invocation of this function
     $el.off('autocomplete:noteselected');
 
+    // Automatically trigger autocomplete on focus, which can achieve:
+    // 1. Automatically display suggestions when $el is focused, without needing to input any text.
+    // 2. Automatically show recent notes when creating a new tab.
+    $el.on('focus', () => {
+        // simulate pressing down arrow to trigger autocomplete
+        const e = $.Event('keydown');
+        e.which = 40; // arrow down
+        $el.trigger(e);
+    });
+
     return $el;
 }